1. Field of the Invention
The present invention relates to a digital TV receiver for processing teletext information, by which a digital TV receives video signals carrying teletext information to display on a screen as intended by a broadcast sender or the teletext information is loaded on an output signal for an external monitor without information loss.
2. Discussion of the Related Art
Lately, previous analog TV receivers are rapidly replaced by digital TV receivers worldwide. In a time of transmission for switching to perfect digital broadcasting, most of the digital TV receivers commercially for sale perfectly support a function of receiving previous analog TV signals as well as digital TV signals. And, the digital TV receiver enables to display the received analog or digital TV signals using a display method of multi-video including main image and sub-image such as PIP, POP, etc,
The analog TV having a long history has received various caption broadcast and the like in various ways to display as well as has provided simple video information photographed by a camera to public viewers via a TV receiver. And, one of them is teletext.
Standardization of the teletext exists in the U.S.-centered 525/60 system, i.e., NTSC broadcasting system, but is variously and powerfully used in the European-centered 625/50 system, i.e. PAL broadcasting system.
FIG. 1 is a diagram showing where general video signal, teletext information, and other synchronization signals are located on 625 lines constructing one frame in analog PAL broadcast signal.
Referring to FIG. 1, teletext information exists on 6˜22 lines and 319˜335 lines.
FIG. 2 shows how the teletext information is loaded on one line where the teletext information can exist concretely. Color burst occurs after initiation of a horizontal synchronization signal. And, information of clock run-in, data and address, and the like follows the color burst according to bit line information value. The information of the clock rub-in, data and address, and the like corresponds to a teletext information value.
FIG. 3 concretely shows what type of waveform the clock run-in forms. Namely, the clock run-in, as shown in FIG. 3 carries data of 2-bytes per 1H, where ‘H’ is a horizontal interval. The data carries clock data, broadcasting station name (e.g., channel data), broadcast programs for several weeks, and the like.
Namely, the teletext information is carried by the above-explained type. A TV receiver receives an analog PAL signal carrying the teletext information, decodes the teletext information, and then displays it, as shown in FIGS. 4A to 4H, on a monitor of the TV receiver. FIGS. 4A to 4H show examples of displaying data broadcast, train and airplane time schedules, various kinds of caption information, and the like on TV screens by real time, respectively.
Specifically, the analog TV for sale in Europe powerfully has implemented a function of various data broadcasts using teletext information. Hence, the digital TV needs to implement teletext information in the same way of the analog TV. Namely, if an input TV signal carries teletext information, it is necessary to detect the teletext information to provide a corresponding image intended by a broadcast sender on a screen or to make the teletext information bypassed to an output signal for an external monitor without distortion.